migrate to django's native JSONField

src/c3nav/site/migrations/0006_django_4_0.py

@@ -0,0 +1,21 @@
+# Generated by Django 4.0.3 on 2022-04-03 17:32
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+        ('site', '0005_siteupdate_default_related_name'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='announcement',
+            name='author',
+            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.PROTECT, to=settings.AUTH_USER_MODEL, verbose_name='author'),
+        ),
+    ]